Accelerator mass spectrometry (AMS) is an accurate analytical technique for measuring extremely low concentrations of numerous long-lived radionuclides. Although it has primarily been used in archaeology and geoscience since its introduction in 1977, AMS is now being used to detect isotopically-labeled biological compounds. Researchers at the Center for Accelerator Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL) first demonstrated this sensitive biomedical tool in 1992 and are currently using it for research in carcinogenesis, mutagenesis, elemental metabolism, immunoassays, dermal transport, and pharmacokinetics. Much of the initial work has been done with 14/C-tagged compounds using an existing system, but they have also demonstrated the sensitive detection tritium (3/H)-labeled samples because of interest in the medical research community in this widely used tracer. When compared to decay counting techniques, 3/H AMS promises a 100 to 1000-fold improvement in detection sensitivity for assaying mg-sized biological samples. The objective of this Phase I study is to demonstrate the feasibility of producing a low cost, compact 3/H AMS based on matching the radio frequency quadrupole (RFQ) linear accelerator (linac) technology available at AccSys to the ion injector and mass spectrometer technology being developed at LLNL. Measurements will be made at the CAMS on the existing laboratory ion injector and spectrometer, in collaboration with researchers at LLNL, in order to provide the design information needed for the RFQ. These measurements will also determine the modifications required to the ion injector and spectrometer for the final design of a turn-key, low-cost 3/H AMS system. Finally, the development cost of the prototype to be demonstrated at the CAMS in Phase II will be estimated, along with the production cost of commercial units. PROPOSED COMMERCIAL APPLICATION: The proposed study will demonstrate the feasibility of a compact AMS accelerator for detecting and quantifying extremely low levels of 3/H from biological samples. Such a dedicated system would make this sensitive diagnostic technique widely available to medical researchers and clinical groups. Research applications include the evaluation of low level toxic agent effects and the monitoring of low doses of pharmaceuticals. Clinical applications include monitoring the effectiveness of radioimmunotherapy and chemotherapy.